Immunohistochemical assessment of progesterone, oestrogen and glucocorticoid receptors in bovine placentomes during pregnancy, induced parturition, and after birth with or without retention of fetal membranes.

Steroid hormones play an important role in placental development. However, the exact cellular site of hormone action has not been evaluated in bovine placentomes. Thus, the present immunohistochemical study was designed to assess the distribution of progesterone receptors, oestrogen receptors and glucocorticoid receptors in bovine placentomes. Tissue specimens were obtained from cows at slaughter and from cattle during pre-term Caesarean section 27 h after prostaglandin administration, immediately after spontaneous parturition and from cattle that had retained the fetal membranes. Specific antibodies were used for receptor demonstration in tissue sections. Progesterone receptors were only detected in maternal connective tissue cells, whereas oestrogen receptors were also present in maternal crypt epithelium. At specific sites, both receptor immunoreactivities remained constant or changed significantly during pregnancy, were generally higher during Caesarean section and decreased post partum, but were less pronounced in cattle that released the fetal membranes than in those that retained the fetal membranes. Glucocorticoid receptors were evident in fetal connective tissue cells as well as in fetal and maternal blood vessels. Maternal crypt epithelial cells showed increasing immunoreactivities for glucocorticoid receptors during pregnancy. Receptor immunoreactivities tended to be lower after spontaneous parturition than during Caesarean section; these results were significant for progesterone and oestrogen receptors in animals that released the fetal membranes but not for those that retained the fetal membranes. The results indicate that in bovine placentome steroid hormone receptors are distributed in patterns that are specific to the type of cell, the stage of pregnancy and the tissue location, implying highly specific modulation of placental metabolism. Retention of the fetal membranes is reflected by altered placental receptor states at parturition.